Technical Field
Embodiments of the subject matter disclosed herein relate to engines. Other embodiments relate to engine diagnostics.
Discussion of Art
Engines may utilize recirculation of exhaust gas from an engine exhaust system to an engine intake system, a process referred to as exhaust gas recirculation (EGR), to reduce regulated emissions. In some examples, a group of one or more cylinders may have an exhaust manifold that is exclusively (and/or selectively) coupled to an intake passage of the engine such that the group of cylinders is dedicated, at least under some conditions, to generating exhaust for EGR. Such cylinders may be referred to as “donor cylinders.” Further, some EGR systems may include multiple valves to direct exhaust to an intake passage and/or an exhaust passage based on a desired amount of EGR. Under some conditions, the multiple valves may become stuck in undesired positions, or may be inadvertently mispositioned. Further still, degradation of one or more of these multiple valves, or other EGR system components, may result in degradation in engine performance and/or eventual engine shutdown.